The present invention relates to the design, fabrication and operation of antennas in general, and, more particularly, to a technique for designing, fabricating and operating antennas that considers the diffusive nature of the environment in which the antennas are to operate.
Although it is not usually difficult to design a workable antenna, it is notoriously difficult to design a good antenna. And while the truthfulness of this statement may be clear for the radio amateur, it is also true for the professional antenna designer who has experience, a state-of-the-art laboratory, and a modern computer with good antenna modeling software.
One of the reasons that a good antenna is difficult to design is that the elements of the antenna interact in a complex and nonlinear manner. Recently, advances in antenna modeling software have made this consideration easier. Another reason is that the objects in the environment in which the antenna operates might scatter the transmitted signal.
FIG. 1 depicts an illustrative terrestrial environment that comprises: transmitting antenna 101, receiving antenna 102, forest 111, building 112, building 113 and boat 114. As a signal is transmitted from transmitting antenna 101 to receiving antenna 102, the signal is likely to be scattered by objects in the environment that are near and between the transmitting antenna and the receiving antenna. A good antenna design considers the scattering of the transmitted signal.
In the prior art, the multipath character of the environment has not, in general, been considered in designing antennas. Rather, designers have usually made the simplifying assumption that the antennas operate in xe2x80x9cfree space.xe2x80x9d FIG. 2 depicts a transmitting antenna and a receiving antenna in free space. When antennas are operating in free space, it is assumed that the transmitted signal radiates without scattering from the transmitting antenna to the receiving antenna. This assumption is perhaps reasonable for terrestrial microwave and satellites, but is untenable for many terrestrial applications (e.g., cities, etc.). The result is that antennas designed and fabricated to operate in free space provide poor performance when operating in diffusive environments. Therefore, the need exists for a technique for designing and fabricating antennas that considers the multipath character of the environment in which the antennas are to operate.
Some embodiments of the present invention are able to design, fabricate and operate antennas without some of the costs and disadvantages of techniques in the prior art. In particular, the illustrative embodiment of the present invention not only considers the multipath character of the environment in which the antennas will operate, but also takes advantage of the scattering to make better antennas. Furthermore, the illustrative embodiment of the present invention can design, fabricate and operate antennas that provide optimal channel capacity by taking advantage of the multipath character of the environment in which the antennas operate.
The illustrative embodiment of the present invention models the multipath character of the environment using diffusive models and uses an iterative approach to predict the performance of candidate antenna designs in that environment and to suggest improvements in the design until the predicted performance reaches an optimal or otherwise acceptable level.
The illustrative embodiment of the present invention comprises: describing an environment; describing a candidate antenna; determining a performance characteristic based on the candidate antenna with respect to the environment; and fabricating a first antenna in accordance with the candidate antenna.